This invention is related to horizontal earth drilling machines of the type in which an auger and a push ring are carried between forward and rearward positions along a set of tracks as the auger progressively drills a horizontal hole in the ground and the push ring pushes a section of pipe into the hole being drilled, and more particularly to such apparatus in which the height of the push ring above the track can be adjusted to accommodate misalignment between the hole being drilled and the desired center line of the hole.
Horizontal earth drilling machines are employed for drilling and inserting a horizontal pipe such as beneath a roadway or the like. The pipe is inserted in standard sections such as 10 or 20 foot lengths. The drilling apparatus is usually inserted in a pit at the inlet of the pipe line and moved between forward and rearward positions. When the carriage is moved to its rearward position, a section of auger is connected between the drill head and the machine, and a section of pipe is mounted with its rearward end engaged by the push ring and its forward end adjacent the hole being drilled. The carriage then advances toward its forward position while the auger drills a hole and the pipe is pushed into the hole being drilled. Upon completion of the drilling stroke, the carriage is returned toward its rearward position so that a new length of auger and a new section of pipe can be mounted between the apparatus and the hole.
One of the problems with drilling such a pipe line, is that usually the outlet of the hole being drilled must precisely intersect another section of pipe installed at the outlet. The centerline of the hole is determined by surveying instruments and periodically checked as the drilled hole progresses.
Under some circumstances such as where the auger encounters rocks or the pipe drifts under pressure, the drilled hole becomes misaligned. The conventional practice is to use a crane to raise the track and place shims under the track in order to realign the carriage so that the pipe is moved along the correct path of motion. This procedure is time-consuming as well as very difficult because of the weight of the equipment and the necessary precision. In addition, it is very costly because of the personnel who are not productively employed while the machine is being shimmed.